Tag: mosquitoes

For a mosquito, venturing out during a heavy rainstorm means risking collisions with droplets 50 times its weight—but this doesn’t deter it from living in humid, rainy climes. In fact, researchers have discovered that the mosquito’s low mass, along with a sturdy exoskeleton, helps it weather (so to speak) the impacts of raindrops without much trouble.

How the Heck:

The researchers confined three-millimeter-long Anopheles mosquitoes in a “drop impact chamber,” an acrylic cage five centimeters wide and twenty centimeters tall. To keep the mosquitoes confined and airborne, a mesh top blocked the insects’ exit while still admitting water droplets, and the cage vibrated once every few seconds to prevent the bugs from landing on the walls.

A high-speed camera filmed the collisions as the researchers either pumped jets of water into the chamber with the speed of a falling raindrop, or released slower droplets to let the camera get a better view. Although a direct body hit could drag the bug down in a five- to twenty-body-length fall before the mosquito escaped the water, droplets tended to hit the mosquitoes’ long wings and legs instead, rolling off their water-repellant bodies and only slightly skewing their flights.

What’s the News: Biochemists at the University of Arizona have found a promising new way to fight disease-carrying mosquitoes. In their research project, published in the journal PNAS, the scientists blocked mosquitoes’ ability to digest blood, making blood-sucking deadly to the winged pests. This technique could someday be used alongside other strategies to battle mosquitoes, like repellents and traps.

As the number of bacteria in mosquitoes’ guts (x axis) went up,
the malaria parasite levels dropped faster than a cartoon anvil.

What’s the News: We know the bacteria living in our guts are important to our health—but the bacteria in mosquitoes’ guts could be too. Researchers have discovered a species of mosquito gut bacteria that destroys the malaria parasite, keeping the disease from spreading to humans. This explains why some Anopheles mosquitoes (the only genus that transmits malaria) don’t spread it, and it spurs the imagination towards possible ways of tamping down the disease.

What’s the News: Forget masking our scent or making us taste bad—sensory overload might be our most potent tool in repelling mosquitoes. And we might someday have a repellent for the job: Scientists have just discovered a molecule that zaps all of a mosquito’s odor receptors at once, overwhelming it. The molecule’s not ready to be deployed yet, but early tests indicate it could be thousands of times more effective than DEET.

What’s the News: When mosquitoes finish a piping-hot meal of blood, they have more than your average postprandial snooze, biologists have found: they go into heat shock, producing proteins most organisms only make when something is terribly wrong.

Selfish genes could help destroy mosquitoes’ ability to carry malaria.

What’s the News: Many scientists have played with the idea of creating a genetically modified mosquito that won’t transmit malaria, which kills about 850,000 people a year, and releasing it into the wild. But in the face of the millions of mosquitoes out there that do ferry malaria around, how would the trait spread fast enough to make a difference?

Now, scientists have developed a way to cause a “selfish” gene to spread to more than half of a mosquito population over just a few generations, suggesting a method to quickly and broadly disrupt genes required for carrying malaria.

Swarms of genetically modified mosquitoes? This isn’t science fiction: The Malaysian government announced earlier this week that it unleashed 6,000 genetically modified (GM) skeeters into a forest as part of a plan to fight dengue fever, a potentially fatal affliction that can affect up to 100 million people each year.

The news appears to have caught the Malaysian media and public by surprise; many recent news stories reported that the study had been postponed after intense protests. As recently as 17 January, the Consumers’ Association of Penang and Sahabat Alam Malaysia, two groups opposing the use of GM insects, called on the National Biosafety Board to revoke its approval for the study. Scientists, too, were under the impression that the work had yet to begin, says medical entomologist Bart Knols of the University of Amsterdam. A 24 January blog post by Mark Benedict, a consultant at the Centers for Disease Control and Prevention in Atlanta who monitors the field closely, mentioned that the Malaysian study was “planned.” [ScienceNOW]

The study itself included the release of 12,000 male mosquitoes in total: 6,000 unaltered and 6,000 GM Aedes aegypti mosquitoes. The goal was to track how well the two types survived and how far they spread. U.K. biotech firm Oxitec created the modified mosquitoes, which don’t produce viable offspring. Researchers hope that if these altered males mate with wild females, it will bring the overall mosquito population down. The strategy has been tried once before in the Grand Cayman Islands, and results from that experiment are due to be published soon.

Researchers from the Imperial College London have a new strategy to combat malaria. The species of mosquito responsible for the spread of malaria in Africa, Anopheles gambiae, only mates once during its life. Putting a stop to their one shot at reproduction should slow down malaria transmission. Anopheles males deploy a glob of proteins and fluids known as a “mating plug” that is essential for ensuring sperm is correctly retained in the female’s sperm storage organ, from where she can fertilise eggs over the course of her lifetime [BBC News]. Without a mating plug, the sperm is not stored and the mosquitoes can’t reproduce.Simply put, the researchers want to prevent male mosquitoes from plugging in the wild.

Anopheles gambiae is the only known species of mosquito to use a mating plug. (However, mating plugs are found in other animals where they prevent multiple males from reproducing with a female. Plug checking mice in research laboratories is a right of passage for many graduate students.) In their research, written up in the journal PLoS Biology, scientists were able to alter the mosquitoes’ genes so that they could no longer form a plug, and thus were unable to reproduce. If this process could be developed for use in the field, perhaps in a spray form like an insecticide, it could “effectively induce sterility in female mosquitoes in the wild,” [study author Flaminia] Catteruccia wrote, offering potential as “one more weapon in the arsenal against malaria” [Reuters]. The WHO is optimistic that their increased funding efforts will produce more technologies similar to this one and that, hopefully, one of them will prove effective.

Amidst concerns over the safety of DEET, scientists are on the lookout for a new mosquito repellent. Now they may have found a way to keep biting insects at bay–by blocking their olfactory sense, according to a paper published in Nature.

Mosquitoes sense the presence of humans and animals by detecting the carbon dioxide we exhale with each breath. Researchers have found two compounds, 2,3-butanedione and 1-hexanol, that could keep the biters at bay by blocking the insects’ ability to detect this gas. Using these compounds could be advantageous because the amount of chemical required is relatively small…. Further, the chemicals themselves are not complicated to manufacture and are available through conventional sources. “From both perspectives, this adds up to a viable tool in tackling the problems like that of malaria in Africa” [Scientific American], says study coauthor Anandasankar Ray. Considering the number of diseases spread by insects such as mosquitoes–for example, 250 million people contract malaria each year–there’s a lot more at stake here than a few itchy bug bites.

Mosquitoes that have made their way to the Galapagos Islands via tourist planes and boats are threatening the rare native species endemic to the region, according to a study published in the journal Proceedings of the Royal Society B.

Culex quinquefasciatus, known as the southern house mosquito, can carry diseases dangerous to wildlife, such as avian pox and West Nile virus. Not only have the insects hopped a ride onto the islands, but they’ve also bred with native species once they reach the shore, the study found. That means they pose an ongoing threat to the Galapagos’ rare species and delicate ecosystem, which inspired Darwin’s theory of evolution after he observed the island’s unique array of wildlife. “You only need a single infectious mosquito to initiate a disease cycle,” [co-author Simon] Goodman…[T]he Galapagos “have globally important biodiversity — endemic species found nowhere else in the world,” said Goodman [Telegraph].